Department of Biomedical Engineering (Y.T., X.G., V.G.F., J.Z., Y.Z.), Heersink School of Medicine, School of Engineering, University of Alabama at Birmingham.
Department of Medicine, Division of Hematology and Oncology (S.A., X.Z., R.L.), Heersink School of Medicine, School of Engineering, University of Alabama at Birmingham.
Circulation. 2022 Nov 15;146(20):1518-1536. doi: 10.1161/CIRCULATIONAHA.122.059713. Epub 2022 Sep 14.
Direct cardiac reprogramming of fibroblasts into cardiomyocytes has emerged as a promising strategy to remuscularize injured myocardium. However, it is insufficient to generate functional induced cardiomyocytes from human fibroblasts using conventional reprogramming cocktails, and the underlying molecular mechanisms are not well studied.
To discover potential missing factors for human direct reprogramming, we performed transcriptomic comparison between human induced cardiomyocytes and functional cardiomyocytes.
We identified (T-box transcription factor 20) as the top cardiac gene that is unable to be activated by the MGT133 reprogramming cocktail (, , , and ). TBX20 is required for normal heart development and cardiac function in adult cardiomyocytes, yet its role in cardiac reprogramming remains undefined. We show that the addition of TBX20 to the MGT133 cocktail (MGT+TBX20) promotes cardiac reprogramming and activates genes associated with cardiac contractility, maturation, and ventricular heart. Human induced cardiomyocytes produced with MGT+TBX20 demonstrated more frequent beating, calcium oscillation, and higher energy metabolism as evidenced by increased mitochondria numbers and mitochondrial respiration. Mechanistically, comprehensive transcriptomic, chromatin occupancy, and epigenomic studies revealed that TBX20 colocalizes with MGT reprogramming factors at cardiac gene enhancers associated with heart contraction, promotes chromatin binding and co-occupancy of MGT factors at these loci, and synergizes with MGT for more robust activation of target gene transcription.
TBX20 consolidates MGT cardiac reprogramming factors to activate cardiac enhancers to promote cardiac cell fate conversion. Human induced cardiomyocytes generated with TBX20 showed enhanced cardiac function in contractility and mitochondrial respiration.
将成纤维细胞直接重编程为心肌细胞，这种方法为修复受损心肌提供了有前景的策略。然而，使用常规的重编程鸡尾酒从人成纤维细胞中产生功能性诱导心肌细胞的效果还不够理想，其潜在的分子机制也尚未得到充分研究。
为了发现人类直接重编程的潜在缺失因子，我们对人诱导心肌细胞和功能性心肌细胞进行了转录组比较。
我们发现 T 盒转录因子 20（T-box transcription factor 20，TBX20）是一种无法被 MGT133 重编程鸡尾酒（包含、、、和）激活的顶级心脏基因。TBX20 对于正常的心脏发育和成年心肌细胞的心脏功能是必需的，但它在心脏重编程中的作用仍未被定义。我们表明，将 TBX20 添加到 MGT133 鸡尾酒（MGT+TBX20）中可促进心脏重编程，并激活与心脏收缩、成熟和心室心脏相关的基因。用 MGT+TBX20 产生的人诱导心肌细胞表现出更频繁的搏动、钙振荡和更高的能量代谢，这表现为线粒体数量和线粒体呼吸的增加。从机制上讲，全面的转录组学、染色质占有率和表观基因组学研究表明，TBX20 与 MGT 重编程因子在与心脏收缩相关的心脏基因增强子处共定位，促进 MGT 因子在这些位点的染色质结合和共占位，并与 MGT 协同作用以更有效地激活靶基因转录。
TBX20 将 MGT 心脏重编程因子整合到一起，激活心脏增强子，以促进心脏细胞命运的转化。用 TBX20 产生的人诱导心肌细胞在收缩性和线粒体呼吸方面表现出增强的心脏功能。
